ADHD

What type of disorder is ADHD classified as in the DSM-5?

A developmental disorder.

What is the essential feature of ADHD?

A persistent pattern of inattention and/or hyperactivity-impulsivity that significantly impacts development.

What are the three types of ADHD diagnoses?

Inattentive type, Hyperactive/Impulsive type, and Combined type.

How long must ADHD symptoms be present for diagnosis?

At least 6 months.

What is the typical age of onset required for diagnosis?

Before age 12.

Name some inattentive symptoms of ADHD.

Distractibility, not listening, not following through on tasks, poor organization, avoiding tasks requiring mental effort, difficulty sustaining attention.

What are additional inattentive symptoms?

Losing things, forgetting daily tasks, careless mistakes, missing details.

Name hyperactive symptoms.

Fidgeting, running/climbing inappropriately, difficulty playing quietly, “on the go,” talking excessively, inability to stay seated.

Name impulsive symptoms.

Blurting out answers, difficulty waiting turn, interrupting or intruding on others.

Why must ADHD symptoms appear in multiple settings?

To ensure the symptoms are not situation-specific (e.g., only at school).

When might ADHD symptoms appear minimal?

Under close supervision, receiving frequent rewards, in a novel setting, or doing something interesting.

What problems commonly result from ADHD?

Academic struggles, social rejection, and comorbid disorders (e.g., ASD, OCD).

Is ADHD an intellectual disability?

No—though mild delays in language, motor, and social skills are common.

What is the worldwide prevalence of ADHD?

Approximately 7.6% (2023 meta-analysis).

What is the male-to-female ratio in ADHD?

About 3:1

What is the prevalence of adult ADHD?

Up to 2.5%

How do ADHD symptoms change over the lifespan?

Hyperactivity/impulsivity decline; attention problems often persist

Why is ADHD diagnosis influenced by culture?

Definitions of problematic behaviour vary by educational expectations and cultural norms

Would ADHD be noticeable in hunter-gatherer societies?

Likely less so due to different expectations for sitting still and maintaining long attention

How common is pure ADHD without other disorders?

Only about one-third of cases.

What condition overlaps genetically and behaviorally with ADHD?

Autism Spectrum Disorder (30–60% show autistic traits).

How heritable is ADHD?

Up to ~80% — one of the most heritable psychiatric disorders.

Which dopamine-related genes show weak associations with ADHD?

The dopamine transporter gene (DAT1) and the D4 receptor gene.

What do newer genetic studies suggest?

ADHD risk genes relate broadly to neurodevelopment.

What is a known gene-environment interaction in ADHD?

Children with a DAT1 mutation + mothers who smoked during pregnancy = higher ADHD risk.

What perinatal factor increases ADHD risk?

Perinatal hypoxia (low oxygen at birth).

Do food dyes/preservatives cause ADHD?

No—except in rare cases of sensitivity.

Does sugar cause ADHD?

No—behavioral effects are consequences, not causes.

How do children with ADHD respond to rewards?

Rewards influence them less strongly than neurotypical children.

What cognitive deficits are common?

Impaired inhibitory control and executive function.

What model explains these deficits?

The Dual Pathway Model (executive dysfunction + reward pathway dysfunction).

This model says ADHD comes from two main problems in the brain:

1. Executive Function Problems

• Trouble with focus, planning, organization, and self-control

• Caused by issues in the frontal lobe
  → Leads to inattention and impulsivity

2. Reward System Problems

• The brain’s dopamine system doesn’t respond strongly to rewards

• People with ADHD prefer immediate rewards and struggle with long, boring tasks
  → Leads to low motivation and seeking stimulation

What is the Default Mode Network (DMN)?

A brain network active during rest/daydreaming.

How is the DMN altered in ADHD?

It fails to deactivate during tasks, causing distractibility.

What is the alerting network, and how is it affected?

It includes frontal-parietal cortex + thalamus; weaker in ADHD.

What is the frontostriatal circuit?

A pathway involving the ACC, putamen, caudate, and nucleus accumbens; abnormal in ADHD.

How effective are ADHD medications?

70–90% effective.

What are common ADHD medications?

Methylphenidate (Ritalin, Concerta), amphetamine (Adderall), d-amphetamine (Dexedrine).

How do these drugs work?

They block the dopamine transporter → increasing dopamine in the synapse.

Why don’t ADHD medications cause a “rush” like illicit stimulants?

They use low doses and slow-release formulations.

Does screen time cause ADHD?

No—but excessive screen time worsens sleep, and poor sleep increases ADHD symptoms.